Apparatus and method to control vacuum at porous material using multiple porous materials

ABSTRACT

An immersion liquid confinement apparatus recovers an immersion liquid from an immersion area that includes a gap between a projection system and an object of exposure in an immersion lithography system. The apparatus includes a confinement member that includes an outlet and an aperture through which a patterned image is projected onto the object. A first liquid-permeable member covers the outlet and has a first surface that faces the object and a second surface opposite the first surface, the second surface contacting a first chamber. A second liquid-permeable member has first and second oppositely-facing surfaces, the first surface of the second liquid-permeable member contacts the first chamber, the second surface of the second liquid-permeable member contacts a second chamber that is different from the first chamber. A hydrophobic porous member is provided between the first chamber and a vacuum system that supplies a low pressure to the first chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation-in-Part of application Ser. No. 12/573,356 filedOct. 5, 2009, which claims the benefit of U.S. Provisional PatentApplication No. 61/193,019 filed Oct. 22, 2008 and claims the benefit ofU.S. Provisional Patent Application No. 61/272,292 filed Sep. 9, 2009.This application claims the benefit of U.S. Provisional Application No.61/272,292 filed Sep. 9, 2009 and of U.S. Provisional Application No.61/272,422 filed Sep. 23, 2009. The disclosures of each of theabove-identified applications is incorporated herein by reference in itsentirety.

BACKGROUND

The invention relates to immersion lithography apparatus and methods,and particularly to apparatus and methods for recovering immersionfluid.

A typical lithography apparatus includes a radiation source, aprojection optical system and a substrate stage to support and move asubstrate to be imaged. A radiation-sensitive material, such as aresist, is coated onto the substrate surface before the substrate isplaced on the substrate stage. During operation, radiation energy fromthe radiation source is used to project an image defined by an imagingelement through the projection optical system onto the substrate. Theprojection optical system typically includes a plurality of lenses. Thelens or optical element closest to the substrate can be referred to asthe last or final optical element.

The projection area during exposure is typically much smaller than thesurface of the substrate. The substrate therefore is moved relative tothe projection optical system in order to pattern the entire surface ofthe substrate. In the semiconductor industry, two types of lithographyapparatus are commonly used. With so-called “step-and-repeat” apparatus,the entire image pattern is projected at one moment in a single exposureonto a target area of the substrate. After the exposure, the substrateis moved or “stepped” in the X and/or Y direction(s) and a new targetarea is exposed. This step-and-repeat process is performed multipletimes until the entire substrate surface is exposed. With scanning typelithography apparatus, the target area is exposed in a continuous or“scanning” motion. For example, when the image is projected bytransmitting light through a reticle or mask, the reticle or mask ismoved in one direction while the substrate is moved in either the sameor the opposite direction during exposure of one target area. Thesubstrate is then moved in the X and/or Y direction(s) to the nextscanned target area. The process is repeated until all of the desiredtarget areas on the substrate have been exposed.

Lithography apparatus are typically used to image or patternsemiconductor wafers and flat panel displays. The word “substrate” asused herein is intended to generically mean any workpiece that can bepatterned including, but not limited to, semiconductor wafers and flatpanel displays.

Immersion lithography is a technique that can enhance the resolution oflithography exposure apparatus by permitting exposure to take place witha numerical aperture (NA) that is greater than the NA that can beachieved in conventional “dry” lithography exposure apparatus having asimilar optical system. By filling the space between the final opticalelement of the projection system and the resist-coated substrate,immersion lithography permits exposure with light that would otherwisebe internally reflected at the optic-air interface. Numerical aperturesas high as the index of the immersion fluid (or of the resist or lensmaterial, whichever is least) are possible in immersion lithographysystems. Liquid immersion also increases the substrate depth-of-focus,that is, the tolerable error in the vertical position of the substrate,by the index of the immersion fluid compared to a dry system having thesame numerical aperture. Immersion lithography thus can provideresolution enhancement without actually decreasing the exposure lightwavelength. Thus, unlike a shift in the exposure light wavelength, theuse of immersion would not require the development of new light sources,optical materials (for the illumination and projection systems) orcoatings, and can allow the use of the same or similar resists asconventional “dry” lithography at the same wavelength. In an immersionsystem in which only the final optical element of the projection systemand its housing and the substrate (and perhaps portions of the stage aswell) are in contact with the immersion fluid, much of the technologyand design developed for dry lithography can carry over directly toimmersion lithography.

However, because the substrate moves rapidly in a typical lithographysystem, the immersion liquid in the immersion area including the spacebetween the projection system and the substrate tends to be carried awayfrom the immersion area. If the immersion liquid escapes from theimmersion area, that liquid can interfere with operation of othercomponents of the lithography system. One way to recover the immersionliquid and prevent the immersion liquid from contaminating the immersionlithography system is described in US2006/0152697 A1, the disclosure ofwhich is incorporated herein by reference in its entirety. Also seeUS2007/0222967 A1, the disclosure of which is incorporated herein byreference in its entirety.

The systems described in US2006/0152697 A1 and US2007/0222967 A1 includean immersion liquid confinement member. The immersion liquid confinementmember includes an outlet through which immersion liquid is recovered(collected) from the immersion area. The outlet is covered by aliquid-permeable member such as a mesh or porous member. A vacuumcontrol unit applies suction to a chamber associated with the outlet soas to draw the immersion liquid on the substrate through theliquid-permeable member and the outlet. It is important to control thesuction force applied to the liquid-permeable member.

SUMMARY

In the systems described above, a lengthy pathway of liquid existsbetween the vacuum control system and the liquid-permeable member thatis disposed to face the substrate (see, for example, FIGS. 6-9 ofUS2006/0152697). The length of the liquid-filled pathway may causedelays in liquid sucking when liquid on the substrate (and/or thesubstrate-holding table) first touches the lower surface of theliquid-permeable member. A long liquid pathway also may cause a largepressure pulse to occur at the liquid-permeable member when the flowrate in the pathway abruptly changes.

U.S. patent application Ser. No. 12/573,356 describes an immersionliquid confinement apparatus that includes first and secondliquid-permeable members to remove liquid from an immersion area thatincludes a gap between a projection system and an object (such as asubstrate, a substrate holding table or both) in an immersionlithography system. The first liquid-permeable member covers an outletin the confinement member and has a first surface that faces the objectand a second surface opposite the first surface and which is in contactwith a first chamber. The second liquid-permeable member is disposed inthe first chamber and includes a first surface that is spaced from andopposes the second surface of the first liquid-permeable member. Thesecond liquid-permeable member also includes a second surface oppositeits first surface. The second surface of the second liquid-permeablemember contacts a second chamber that is different from the firstchamber.

In the apparatus of U.S. patent application Ser. No. 12/573,356, firstand second vacuum systems are respectively coupled to the first andsecond chambers. The first vacuum system, coupled to the first chamber,draws the immersion liquid from the immersion area into the firstchamber through the first liquid-permeable member so that the liquidflows from the first surface of the first liquid-permeable member to thesecond surface of the first liquid-permeable member. Preferably, liquidis not conveyed from the first chamber to the first vacuum system.Therefore, there is no lengthy liquid pathway between the firstliquid-permeable member and the first vacuum system. The second vacuumsystem is coupled to the second chamber and draws liquid from the firstchamber through the second liquid-permeable member into the secondchamber such that the liquid flows through the second liquid-permeablemember from its first surface to its second surface.

The second vacuum system also draws the immersion liquid from the secondchamber so that the liquid can be disposed of and/or recycled andresupplied to the immersion area through, for example, an immersionliquid supply system. Although there may be a lengthy liquid pathwaybetween the second vacuum system and the second liquid-permeable member,because the second liquid-permeable member does not directly face theobject (substrate, substrate table, etc.), the pressure fluctuationcaused by the change in flow through the second liquid-permeable memberwould not affect the pressure in the first chamber.

As noted above, it is preferable, in fact highly desirable, that liquidis not conveyed from the first chamber to the first vacuum system. Ifliquid enters the connecting path between the first chamber and thefirst vacuum system, the vacuum regulator of the first vacuum systemwould not be able to accurately control the vacuum pressure within thefirst chamber. One way to avoid or inhibit liquid entering theconnecting path, which typically is a tube or a channel connecting thefirst chamber to the first vacuum system, is to design the connectingpath with a relatively large cross-section so that any liquid enteringthe path could easily fall back into the first chamber. Another optionis to place the port where the connecting path communicates with thefirst chamber high up within the chamber and to carefully control theliquid level within the first chamber so that the liquid never touchesthe port. Both of these options limit the design of the confinementmember and tend to increase its size.

According to aspects of the invention, a hydrophobic porous member isplaced at the connecting path to prevent liquid from traveling from thefirst chamber to the first vacuum system. Preferably the hydrophobicporous member is placed at the entrance port of the connecting path sothat the liquid remains in the first chamber. The expression“hydrophobic” as used herein is intended to mean “repels liquid”, and isnot limited to materials that repel water (that is, “hydro” is intendedto encompass many liquids, not only water).

The size of the pores and the hydrophobicity of the hydrophobic materialof the hydrophobic porous member are selected such that the low pressure(vacuum) provided by the first vacuum system will be insufficient topull (suck) the immersion liquid through the hydrophobic porous member.Thus, only gas passes through the hydrophobic porous member. Liquid willnot pass through the hydrophobic porous member when the first vacuumsystem applies its vacuum through the connecting path to the firstchamber.

Using the hydrophobic porous member will permit the cross-section of theconnecting path between the first chamber and the first vacuum system tobe minimized, which can enable the size of the confinement member to bereduced. The size of the confinement member also can be reduced becausethe hydrophobic porous member (and thus the entrance port of theconnecting path) can be located at many more places within the firstchamber, including places that may become submerged in the liquid withinthe first chamber.

Other aspects of the invention relate to an immersion lithographyapparatus having a projection system, a movable stage that is movable toa position below the projection system and that holds an object such asa substrate, and a confinement member according to aspects of theinvention.

Other aspects of the invention relate to methods of manufacturingdevices using the immersion lithography apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings of exemplary embodiments in which like reference numeralsdesignate like elements, and in which:

FIG. 1 is a simplified elevational view schematically illustrating animmersion lithography system according to some embodiments of theinvention;

FIG. 2 is a simplified side cross-sectional view of a liquid confinementmember and its fluid removal system according to a first embodiment ofthe invention;

FIG. 3 is a simplified side cross-sectional view of a liquid confinementmember and its fluid removal system according to a second embodiment ofthe invention;

FIG. 4 is a simplified side cross-sectional view of a liquid confinementmember and its fluid removal system according to a third embodiment ofthe invention;

FIG. 5 is a flowchart that outlines a process for manufacturing a devicein accordance with the invention; and

FIG. 6 is a flowchart that outlines device processing in more detail.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an immersion lithography system 10 including a reticlestage 12 on which a reticle is supported, a projection system 14 havinga last or “final” optical element 16, and a fine-movement stage 22 onwhich a substrate 26 is supported, which in turn is movable over acoarse-movement stage 20. An immersion liquid supply and recoveryapparatus 18, which is sometimes referred to herein as a liquidconfinement member 18, is disposed around the final optical element 16of the projection system 14 so as to supply and recover an immersionfluid, which may be a liquid such as, for example, water, to/from a gap28 between the final optical element 16 and the substrate 26. In thepresent embodiment, the immersion lithography system 10 is a scanninglithography system in which the reticle and the substrate 26 are movedsynchronously in respective scanning directions during a scanningexposure operation. The fine-movement stage 22 controls the position ofthe substrate 26 in one or more (preferably all) of the X, Y, Z, θX, θYand θZ directions with a higher degree of precision than thecoarse-movement stage 20, which is primarily used for moving thesubstrate 26 over longer distances, as is well known in the art. Theupper surface of the fine movement stage 22 includes a substrate holderthat preferably has a recess that holds the substrate 26. In addition, aportion of the upper surface of the fine movement stage 22 thatsurrounds the held substrate has an upper surface that is substantiallylevel with the upper surface of the held substrate so that when theimmersion area is located near the edge of the substrate, liquid isstill maintained between the liquid confinement member 18 and the uppersurfaces of the substrate 26 and of the substrate holder.

The illumination source of the lithography system can be a light sourcesuch as, for example, a mercury g-line source (436 nm) or i-line source(365 nm), a KIT excimer laser (248 nm), an ArF excimer laser (193 nm) ora F₂ laser (157 nm). The projection system 14 projects and/or focusesthe light passing through the reticle onto the substrate 26. Dependingupon the design of the exposure apparatus, the projection system 14 canmagnify or reduce the image illuminated on the reticle. It also could bea 1× magnification system.

When far ultraviolet radiation such as from the excimer laser is used,glass materials such as silica glass and calcium fluoride that transmitfar ultraviolet rays can be used in the projection system 14. Theprojection system 14 can be catadioptric, completely refractive orcompletely reflective.

With an exposure device, use of the catadioptric type optical system canbe considered. Examples of the catadioptric type of optical system areshown in U.S. Pat. No. 5,668,672 and U.S. Pat. No. 5,835,275. In thesecases, the reflecting optical device can be a catadioptric opticalsystem incorporating a beam splitter and concave mirror. U.S. Pat. No.5,689,377 also uses a reflective-refracting type of optical systemincorporating a concave mirror, etc., but without a beam splitter, andalso can be employed with this invention. The disclosures of theabove-mentioned U.S. patents are incorporated herein by reference intheir entireties.

FIG. 2 is a cross-section view of an embodiment of a liquid confinementmember 18. As shown in FIG. 2, the liquid confinement member 18maintains immersion liquid 80 in an immersion area, which includes thegap or space between the final optical element 16 of the projectionsystem 14 and a portion of the upper surface of the substrate 26. Theimmersion liquid 80 in FIG. 2 can be seen as occupying only a portion ofthe upper surface of the substrate 26. That is, the size of theimmersion area is smaller than the size of the upper surface of thesubstrate 26 such that only part of the upper surface of the substrateis covered. Depending on the relative position of the substrate 26 withrespect to the projection system 14 (and the liquid confinement member18) the immersion area can be disposed over the substrate, over aportion of the substrate and a portion of the substrate holder thatsurrounds the substrate, or over only a portion of the substrate holder(for example, when the substrate is moved such that it no longer isdisposed below the projection system 14). In addition, if the exposureapparatus includes a measurement stage that is used to take measurementsregarding the projection system 14, the immersion area can be formedbetween an upper surface of the measurement stage and the final opticalelement 16 (there would be no substrate holder on the measurementstage).

The liquid confinement member 18 includes at least one (and preferablymore than one) liquid supply inlets 30 through which the immersionliquid 80 is supplied to the immersion area. The liquid is supplied tothe supply inlets 30 through a supply path, one end of which isconnected to a liquid supply 15 and the other end of which is connectedto an inlet manifold of the liquid confinement member 18. The liquidsupplied to the supply inlets 30 reaches the substrate 26 after passingthrough aperture 35 disposed centrally in the confinement member 18. Asshown in FIG. 2, the supply and recovery of the immersion liquid iscontrolled so that the level of the immersion liquid between the liquidconfinement member 18 and the final optical element 16 is maintainedabove the lower surface of the final optical element 16 so that theexposure light transmitted through the projection system 14 travels onlythrough the immersion liquid (that is, the exposure light does nottravel through any air or gas) before reaching the substrate 26.

In the FIG. 2 embodiment, the liquid confinement member 18 includes anoutlet 40. In the FIG. 2 embodiment, the outlet 40 is an annular groovethat surrounds aperture 35, and thus also surrounds the immersion area.Liquid is removed from the immersion area and from the surface of thesubstrate 26 (and/or the surface of the substrate holder) via the outlet40. The outlet 40 is covered by a first liquid-permeable member 52 suchthat a first chamber 42 is disposed at least partially within the liquidconfinement member 18. A first (lower) surface of the firstliquid-permeable member 52 faces toward the substrate 26, whereas asecond (upper) surface of the first liquid-permeable member 52 contactsthe chamber 42. Liquid that passes through the first liquid-permeablemember 52 from its first surface to its second surface thus enters thefirst chamber 42.

Although the outlet 40 (and thus also the first liquid-permeable member52) is a continuous groove in FIG. 2, the outlet 40 (and thus the firstliquid-permeable member 52 covering the outlet) could be a series ofarc-shaped portions, straight portions or angled portions thatcollectively surround the immersion area and communicate with firstchamber 42. Furthermore, the outlet could be circular in plan view,rectangular or any other shape in plan view.

A second liquid-permeable member 54 is disposed within first chamber 42and includes a first (lower) surface that is spaced from and faces thesecond (upper) surface of the first liquid-permeable member 52. Thesecond liquid-permeable member 54 also includes a second (upper) surfaceopposite its first surface and that contacts a second chamber 60. Thesecond chamber 60 thus is defined by the second liquid-permeable member54 and walls or other structure.

The first chamber 42 communicates with a first vacuum system V1 thatapplies a suction force to the first chamber 42. The suction force issufficient to draw immersion liquid through the first liquid-permeablemember 52 into the first chamber 42. The first vacuum system V1 iscontrolled so that the suction force applied to the firstliquid-permeable member 52 is maintained below the bubble point of thefirst liquid-permeable member 52. That is, the first vacuum system V1controls a pressure in the first chamber 42 such that substantially onlyliquid is removed from the immersion area and/or from the surface of thesubstrate 26 (and/or the surface of the substrate holder) through thefirst liquid-permeable member 52, but not gas from the surface of thesubstrate 26 (and/or the surface of the substrate holder). However, thefirst vacuum system V1 does not cause the liquid to be removed fromfirst chamber 42.

Rather, a second vacuum system V2 that communicates with the secondchamber 60 causes liquid within the first chamber 42 to be drawn throughthe second liquid-permeable member 54 into the second chamber 60. Theliquid within the second chamber 60 is then removed from the secondchamber 60 via the suction force caused by second vacuum system V2. Thesecond vacuum system V2 is controlled so that the suction force appliedto the second liquid-permeable member 54 is maintained below the bubblepoint of the second liquid-permeable member 54. That is, the secondvacuum system V2 controls a pressure in the second chamber 60 such thatsubstantially only liquid is removed from the first chamber 42 throughthe second liquid-permeable member 54, but not gas from the firstchamber 42. The vacuum systems V1 and V2 can be systems for controllinga vacuum force as described, for example, in US2006/0152697 A1 andUS2007/0222967 A1, the disclosures of which are incorporated herein byreference in their entireties.

As noted above, it is highly desirable that liquid is not conveyed fromthe first chamber 42 to the first vacuum system V1. If liquid enters theconnecting path 90 between the first chamber 42 and the first vacuumsystem V1, the vacuum regulator (not shown) of the first vacuum systemV1 would not be able to accurately control the vacuum pressure withinthe first chamber 42. One way to avoid or inhibit liquid entering theconnecting path 90, which typically is a tube or a channel connectingthe first chamber 42 to the first vacuum system V1, is to design theconnecting path 90 with a relatively large cross-section so that anyliquid entering the path 90 could easily fall back into the firstchamber 42. For example, the cross-section of the connecting path, whenno hydrophobic porous member is provided, should be at least 8 mm.Another option is to place the port 92 where the connecting path 90communicates with the first chamber 42 high up within the chamber 42 andto carefully control the liquid level within the first chamber 42 sothat the liquid never touches the port 92. Both of these options limitthe design of the confinement member 18 and tend to increase its size.

Accordingly, a hydrophobic porous member 96 is placed at the connectingpath 90 to prevent liquid from traveling from the first chamber 42 tothe first vacuum system V1. Preferably the hydrophobic porous member 96is placed at the entrance port 92 of the connecting path 90 so that theliquid remains in the first chamber 42. The expression “hydrophobic” asused herein is intended to mean “repels liquid”, and is not limited tomaterials that repel water (that is, “hydro” is intended to encompassmany liquids, not only water).

According to one embodiment, the hydrophobic porous member 96 is aporous body of polytetrafluoroethylene (Teflon™), or is a porous bodyhaving surfaces coated with polytetrafluoroethylene, although othermaterials that are hydrophobic with respect to the immersion liquid 80can be used. Other hydrophobic materials include, for example,perfluoroalkoxy (PFA) and fluorinated ethylene propylene (FEP). The sizeof the pores could range from 1-150 μm in diameter, for example. Becauseof the hydrophobicity and the small diameter of the pores, immersionliquid 80 would not be able to enter the pores unless the pressurecontrolled by first vacuum system V1 is lower than the pressure causedby the repulsive capillary force between the hydrophobic pores and theimmersion liquid 80. The pressure caused by the repulsive capillaryforce can be calculated by the following equation:

Bubble point pressure=2γ cos θ/r,

where

-   -   γ=surface tension of the immersion liquid,    -   θ=contact angle of immersion liquid on the hydrophobic member,    -   r=radius of the largest pore in the hydrophobic member.

When choosing the material of the hydrophobic member 96, the propertiesof the member (pore size and hydrophobicity) should be considered sothat the required pressure inside the first chamber 42 is higher thanthe pressure caused by the repulsive capillary force between the liquidand the hydrophobic member 96. That is, the size of the pores and thehydrophobicity of the hydrophobic material of the hydrophobic porousmember 96 are selected such that the low pressure (vacuum) provided bythe first vacuum system V1 will be insufficient to pull (suck) theimmersion liquid through the hydrophobic porous member 96. Thus, onlygas passes through the hydrophobic porous member 96. Liquid will notpass through the hydrophobic porous member 96 when the first vacuumsystem V1 applies its vacuum through the connecting path 90 to the firstchamber 42.

The manner in which the liquid confinement member 18 is controlled toremove liquid now will be described.

For context, a system such as the system described in US2006/0152697 A1will be described. The system of US2006/0152697 A1 is similar to what isshown in FIG. 2 of the present application except that there is nosecond chamber 60, second liquid-permeable member 54, second vacuumcontrol system V2, or hydrophobic porous member 96. The system ofUS2006/0152697 A1 simply draws immersion liquid through a singleliquid-permeable member such as the first liquid-permeable member 54shown in Applicants' FIG. 2. The liquid fills a single chamber, such asfirst chamber 42, and the liquid is drawn from chamber 42 by a singlevacuum system such as system V1 of Applicants' FIG. 2. Accordingly,there is a lengthy liquid pathway between the vacuum system and theliquid-permeable member that faces the substrate. Therefore, asmentioned earlier, when liquid initially contacts the lower surface ofthe liquid-permeable member, there is a delay in the recovery of thatliquid due to the time required to accelerate the liquid in the lengthyliquid pathway. In addition, the long liquid pathway causes a largepressure pulse to occur when the flow rate in the pathway changesabruptly, which occurs, for example, when exposure begins and ends foreach substrate and when rapid movements of the substrate occur, forexample, between the exposure of different shot areas on the substrate.Accordingly, to avoid exceeding the bubble point at the liquid-permeablemember, the suction force provided by the vacuum control systemtypically is reduced substantially below the suction force that wouldexceed the bubble point of the liquid-permeable member. Thus, even whenthere are pressure pulses, the vacuum force will not exceed the bubblepoint of the liquid-permeable member. Reducing the suction force,however, further reduces the responsiveness of the liquid recoverysystem, for example, when liquid initially touches the liquid-permeablemember. This can cause liquid to escape from below the liquidconfinement member. Reducing the suction force also reduces the maximumflow rate by which the liquid can be collected. For example, in a systemwhere the bubble point of the liquid-permeable member is 2 KPascal, thevacuum control system may be controlled so that the steady state suctionforce applied to the liquid-permeable member is about 1 KPascal.

In the system described in Applicants' FIG. 2, a suction force muchcloser to the bubble point of the first liquid-permeable member can beapplied to the first-liquid permeable member by first vacuum controlsystem V1 because there is a very short liquid path above the firstliquid-permeable member 52 in the first chamber 42. In particular, thelength of the liquid path is approximately equal to the distance betweenthe lower surface of the second liquid-permeable member 54 and the uppersurface of the first liquid-permeable member 52. This distance can be assmall as 3 mm.

Because there is a short liquid path formed above the firstliquid-permeable member 52, there is substantially no delay in liquidsucking when liquid first touches the lower surface of the firstliquid-permeable member 52. Furthermore, the short liquid pathway formedabove the first liquid-permeable member 52 will not cause large pressurepulse to occur when the flow rate in that pathway changes abruptly.Accordingly, the first vacuum control system V1 can be controlled so asto apply a suction force to the first liquid-permeable member that isvery close to the bubble point of the first liquid-permeable member 52.Thus, the conditions occurring at the first liquid-permeable member 52are very stable regardless of the rate of liquid flow through the firstliquid-permeable member 52.

In addition, the hydrophobic porous member 96 will prevent the firstvacuum system V1 from becoming fouled with immersion liquid, and willpermit the cross-section of the connecting path 90 between the firstchamber 42 and the first vacuum system V1 to be minimized, which canenable the size of the confinement member 18 to be reduced. The size ofthe confinement member 18 also can be reduced because the hydrophobicporous member 96 (and thus the entrance port 92 of the connecting path90) can be located at many more places within the first chamber 42,including places that may become submerged in the liquid within thefirst chamber 42.

The control of flow through the second liquid-permeable member 54 issimilar to what was described above with respect to the control of flowthrough a system having a single liquid-permeable member. In particular,the suction force applied by second vacuum control system V2 to thesecond liquid-permeable member 54 maintains the suction force at thesecond liquid-permeable member 54 far enough below the bubble point ofthe second liquid-permeable member 54 so that large pressure pulses thatmay occur at the second liquid-permeable member 54 when there are abruptchanges in liquid flow do not exceed the bubble point of the secondliquid-permeable member 54. When there are large changes in flow,however, the excess liquid, which cannot initially be drawn fast enoughthrough the second liquid-permeable member 54 is accommodated within thefirst chamber 42 (that is, the liquid level within first chamber 42 willrise when there is a sudden increase in flow through the firstliquid-permeable member 52). However, once that surge in flow reducesand the flow through the second liquid-permeable member 54 reaches amore steady state, the level of liquid within the first chamber 42 willgradually decrease until it reaches the steady condition shown in FIG.2.

Although the second liquid-permeable member 54 in FIG. 2 is shown asarranged substantially horizontal, it is preferable that the secondliquid-permeable member 54 be arranged so that it is not horizontalalong its entire surface because air bubbles may get trapped under thelower surface of a flat horizontal member 54 when the liquid flow islow. Accordingly, alternative embodiments shown in FIGS. 3 and 4 providea second liquid-permeable member in which a distance between the lowersurface of the second liquid-permeable member and the upper surface ofthe first liquid-permeable member varies for different portions of thesecond liquid-permeable member.

FIG. 3 shows an embodiment in which the second liquid-permeable member54 a is slanted so that one portion of it is closer to the firstliquid-permeable member 52 than is another portion of the secondliquid-permeable member 54 a.

FIG. 4 shows an embodiment in which the second liquid-permeable member54 b is convex so that different portions of it are spaced differentdistances from the first liquid-permeable member 52. In addition, FIG. 4shows a modification in which the connecting path 90 between the firstchamber 42 and the first vacuum system V1 is at least partially placedwithin the connecting path between the second chamber 60 and the secondvacuum system V2. This modification reduces the number of connectionsbetween the confinement member 18 and the vacuum systems because asingle (dual lumen) connection passage is provided between theconfinement member 18 and the vacuum systems. Such a modification isfacilitated by the hydrophobic member 96 because the hydrophobic member96 enables the diameter of the connecting path 90 to be reduced. Themodification shown in FIG. 4 also can be applied to the embodimentsshown in FIGS. 2 and 3.

The embodiments of FIGS. 3 and 4 also are advantageous in that they canmore readily accommodate changes in flow through the firstliquid-permeable member 52 because, as the flow rate increases, morearea of the second liquid-permeable member 54 a or 54 b will come intocontact with the liquid in chamber 42, thereby increasing the flow ratecapacity through the second liquid-permeable member 54 a/54 b.

In certain embodiments, the immersion fluid is a liquid having a highindex of refraction. In different embodiments, the liquid may be purewater, or a liquid including, but not limited to, cedar oil,fluorin-based oils, “Decalin” or “Perhydropyrene.”

The first liquid-permeable member 52, or the second liquid-permeablemember 54, or both of the first and second liquid-permeable members maybe a porous member such as a mesh or may be formed of a porous materialhaving holes typically with a size smaller than 150 μm. For example, theporous member may be a wire mesh including woven pieces or layers ofmaterial made of metal, plastic or the like, a porous metal, a porousglass, a porous plastic, a porous ceramic, a sponge or a sheet ofmaterial having chemically etched holes (for example, by photo-etching).The first and second liquid-permeable members could be identical instructure or could differ in one or more of pore size, thickness andporosity. In certain embodiments, the first vacuum system V1 may becontrolled so that the suction force applied to the firstliquid-permeable member 52 is maintained at or above the bubble point ofthe first liquid-permeable member 52. That is, the first vacuum systemV1 may control a pressure in the first chamber 42 such that a mixture ofliquid and gas is removed from the immersion area and/or from thesurface of the substrate 26 (and/or the surface of the substrate holder)through the first liquid-permeable member 52. In certain embodiments,the second vacuum system V2 may be controlled so that the suction forceapplied to the second liquid-permeable member 54 is maintained at orabove the bubble point of the second liquid-permeable member 54. Thatis, the second vacuum system V2 may control a pressure in the secondchamber 60 such that a mixture of liquid and gas is removed from thefirst chamber 42 through the second liquid-permeable member 54.

The use of the exposure apparatus described herein is not limited to aphotolithography system for semiconductor manufacturing. The exposureapparatus, for example, can be used as an LCD photolithography systemthat exposes a liquid crystal display device pattern onto a rectangularglass plate, or a photolithography system for manufacturing a thin filmmagnetic head.

Semiconductor devices can be fabricated using the above describedsystems, by the process shown generally in FIG. 5. In step 801 thedevice's function and performance characteristics are designed. Next, instep 802, a mask (reticle) having a pattern is designed according to theprevious designing step, and in a step 803, a wafer is made from asilicon material. The mask pattern designed in step 802 is exposed ontothe wafer from step 803 in step 804 by a photolithography systemdescribed hereinabove in accordance with aspects of the invention. Instep 805, the semiconductor device is assembled (including the dicingprocess, bonding process and packaging process). Finally, the device isthen inspected in step 806.

FIG. 6 illustrates a detailed flowchart example of the above-mentionedstep 804 in the case of fabricating semiconductor devices. In FIG. 6, instep 811 (oxidation step), the wafer surface is oxidized. In step 812(CVD step), an insulation film is formed on the wafer surface. In step813 (electrode formation step), electrodes are formed on the wafer byvapor deposition. In step 814 (ion implantation step), ions areimplanted in the wafer. The above mentioned steps 811-814 form thepreprocessing steps for wafers during wafer processing, and selection ismade at each step according to processing requirements.

At each stage of wafer processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 815(photoresist formation step), photoresist is applied to a wafer. Next,in step 816 (exposure step), the above-mentioned exposure device is usedto transfer the circuit pattern of a mask (reticle) to a wafer. Then instep 817 (developing step), the exposed wafer is developed, and in step818 (etching step), parts other than residual photoresist (exposedmaterial surface) are removed by etching. In step 819 (photoresistremoval step), unnecessary photoresist remaining after etching isremoved. Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

A photolithography system (an exposure apparatus) according to theembodiments described herein can be built by assembling varioussubsystems in such a manner that prescribed mechanical accuracy,electrical accuracy, and optical accuracy are maintained. In order tomaintain the various accuracies, prior to and following assembly, everyoptical system is adjusted to achieve its optical accuracy. Similarly,every mechanical system and every electrical system are adjusted toachieve their respective mechanical and electrical accuracies. Theprocess of assembling each subsystem into a photolithography systemincludes providing mechanical interfaces, electrical circuit wiringconnections and air pressure plumbing connections between eachsubsystem. Each subsystem also is assembled prior to assembling aphotolithography system from the various subsystems. Once aphotolithography system is assembled using the various subsystems, atotal adjustment is performed to make sure that accuracy is maintainedin the complete photolithography system. Additionally, it is desirableto manufacture an exposure system in a clean room where the temperatureand cleanliness are controlled.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. The invention isintended to cover various modifications and equivalent arrangements. Inaddition, while the various elements of the preferred embodiments areshown in various combinations and configurations, that are exemplary,other combinations and configurations, including more, less or only asingle element, are also within the spirit and scope of the invention.

1. An immersion liquid confinement apparatus for confining an immersionliquid in an immersion area that includes a gap between a projectionsystem and an object of exposure in an immersion lithography system, theapparatus also recovering the immersion liquid from the immersion area,the apparatus comprising: a confinement member that includes an outletand an aperture through which a patterned image is projected onto theobject; a first liquid-permeable member covering the outlet and having afirst surface that faces the object and a second surface opposite thefirst surface, the second surface contacting a first chamber; a secondliquid-permeable member disposed adjacent to and spaced from the secondsurface of the first liquid-permeable member, the secondliquid-permeable member having a first surface that faces the secondsurface of the first liquid-permeable member and a second surfaceopposite the first surface of the second liquid-permeable member, thesecond surface of the second liquid-permeable member contacting a secondchamber that is different from the first chamber; and an entrance portof the first chamber through which the first chamber is communicatedwith a vacuum system, a hydrophobic porous member covering the entranceport.
 2. The apparatus of claim 1, wherein a pore size of pores of thehydrophobic porous member is 1-150 μm.
 3. The apparatus of claim 1,wherein the hydrophobic porous member is porous polytetrafluoroethylene,porous perfluoroalkoxy, or porous fluorinated ethylene propylene.
 4. Theapparatus of claim 1, wherein the entrance port is a first lumen of adual-lumen passage, a second lumen of the dual-lumen passage comprisinga second entrance port by which the second chamber is connected to asecond vacuum system.
 5. The apparatus of claim 1, wherein a distancebetween the second liquid-permeable member and the first liquidpermeable member varies for different portions of the first surface ofthe second liquid-permeable member.
 6. The apparatus of claim 5, whereinthe first surface of the second liquid-permeable member is convex. 7.The apparatus of claim 5, wherein the second liquid-permeable member isslanted relative to the first liquid-permeable member.
 8. The apparatusof claim 1, wherein at least one of the first and secondliquid-permeable members is a mesh.
 9. The apparatus of claim 1, whereinat least one of the first and second liquid-permeable members is asponge.
 10. The apparatus of claim 1, wherein at least one of the firstand second liquid-permeable members is a plate have holes extendingthrough the plate.
 11. An immersion liquid confinement apparatus forconfining an immersion liquid in an immersion area that includes a gapbetween a projection system and an object of exposure in an immersionlithography system, the apparatus also recovering the immersion liquidfrom the immersion area, the apparatus comprising: a confinement memberthat includes an outlet and an aperture through which a patterned imageis projected onto the object; a first liquid-permeable member coveringthe outlet and having a first surface that faces the object and a secondsurface opposite the first surface, the second surface contacting afirst chamber; a second liquid-permeable member having first and secondoppositely-facing surfaces, the first surface of the secondliquid-permeable member contacts the first chamber, the second surfaceof the second liquid-permeable member contacts a second chamber that isdifferent from the first chamber; and an entrance port of the firstchamber through which the first chamber is communicated with a vacuumsystem, a hydrophobic porous member covering the entrance port.
 12. Theapparatus of claim 11, wherein a pore size of pores of the hydrophobicporous member is 1-150 μm.
 13. The apparatus of claim 11, wherein thehydrophobic porous member is porous polytetrafluoroethylene, porousperfluoroalkoxy, or porous fluorinated ethylene propylene.
 14. Theapparatus of claim 11, wherein the entrance port is a first lumen of adual-lumen passage, a second lumen of the dual-lumen passage comprisinga second entrance port by which the second chamber is connected to asecond vacuum system.
 15. The apparatus of claim 11, wherein the firstliquid-permeable member is horizontally disposed, and the first surfaceof the second liquid-permeable member is disposed at a position that isvertically spaced from the second surface of the first liquid-permeablemember.
 16. The apparatus of claim 15, wherein a vertical distancebetween the first surface of the second liquid-permeable member and thesecond surface of the first liquid permeable member varies for differentportions of the first surface of the second liquid-permeable member. 17.The apparatus of claim 16, wherein the first surface of the secondliquid-permeable member is convex.
 18. The apparatus of claim 16,wherein the second liquid-permeable member is slanted relative to thefirst liquid-permeable member.
 19. The apparatus of claim 11, wherein atleast one of the first and second liquid-permeable members is a mesh.20. The apparatus of claim 11, wherein at least one of the first andsecond liquid-permeable members is a sponge.
 21. The apparatus of claim11, wherein at least one of the first and second liquid-permeablemembers is a plate have holes extending through the plate.
 22. Animmersion lithography apparatus comprising: a projection system having afinal optical element; a movable stage that is movable to a positionbelow the projection system such that a gap exists between the finaloptical element and a surface of the stage, an immersion liquid beingfilled in the gap between the surface and the final optical element; anda confinement member that maintains the immersion liquid in the gapbetween the surface and the final optical element, the confinementmember including: an outlet; an aperture through which a patterned imageis projected by the projection system through the immersion liquid ontothe movable stage; a first liquid-permeable member covering the outletand having a first surface that faces the surface of the stage and asecond surface opposite the first surface, the second surface contactinga first chamber; a second liquid-permeable member disposed adjacent toand spaced from the second surface of the first liquid-permeable member,the second liquid-permeable member having a first surface that faces thesecond surface of the first liquid-permeable member and a second surfaceopposite the first surface of the second liquid-permeable member, thesecond surface of the second liquid-permeable member contacting a secondchamber that is different from the first chamber; and an entrance portof the first chamber through which the first chamber is communicatedwith a vacuum system, a hydrophobic porous member covering the entranceport.
 23. The apparatus of claim 22, wherein a pore size of pores of thehydrophobic porous member is 1-150 μm.
 24. The apparatus of claim 22,wherein the hydrophobic porous member is porous polytetrafluoroethylene,porous perfluoroalkoxy, or porous fluorinated ethylene propylene. 25.The apparatus of claim 22, further comprising: a first vacuum systemcoupled to the entrance port of the first chamber so as to draw theimmersion liquid into the first chamber through the firstliquid-permeable member from the first surface of the firstliquid-permeable member to the second surface of the firstliquid-permeable member.
 26. The apparatus of claim 25, furthercomprising: a second vacuum system coupled to an entrance port of thesecond chamber, the immersion liquid being drawn from the first chamberthrough the second liquid-permeable member into the second chamber bythe second vacuum system.
 27. The apparatus of claim 26, wherein theentrance port of the first chamber is a first lumen of a dual-lumenpassage, a second lumen of the dual-lumen passage comprising theentrance port of the second chamber.
 28. The apparatus of claim 22,wherein a distance between the second liquid-permeable member and thefirst liquid permeable member varies for different portions of the firstsurface of the second liquid-permeable member.
 29. The apparatus ofclaim 28, wherein the first surface of the second liquid-permeablemember is convex.
 30. The apparatus of claim 28, wherein the secondliquid-permeable member is slanted relative to the firstliquid-permeable member.
 31. The apparatus of claim 22, wherein at leastone of the first and second liquid-permeable members is a mesh.
 32. Theapparatus of claim 22, wherein at least one of the first and secondliquid-permeable members is a sponge.
 33. The apparatus of claim 22,wherein at least one of the first and second liquid-permeable members isa plate have holes extending through the plate.
 34. The apparatus ofclaim 22, wherein the confinement member substantially surrounds thefinal optical element of the projection system.
 35. The apparatus ofclaim 22, wherein the stage includes a substrate holder, and an uppersurface of the substrate holder, an upper surface of a substrate held bythe substrate holder, or both, corresponds to the surface between whichthe gap is formed with the final optical element.
 36. A devicemanufacturing method comprising: exposing a substrate by projecting apattern image onto the substrate through an immersion liquid and theprojection system of the apparatus of claim 22; and developing theexposed substrate.
 37. A method of recovering immersion liquid from animmersion area that includes a gap between a projection system and anobject of exposure in an immersion lithography system, the methodcomprising: drawing the immersion liquid from the immersion area thougha first liquid-permeable member into a first chamber disposed at leastpartly within a confinement member that includes an outlet and anaperture through which a patterned image is projected onto the object,the outlet including the first liquid-permeable member which covers theoutlet, the first liquid-permeable member having a first surface thatfaces the object and a second surface opposite the first surface, thesecond surface contacting the first chamber, a hydrophobic porous membercovering an entrance port by which the first chamber is communicatedwith a vacuum system; and drawing the immersion liquid from the firstchamber through a second liquid-permeable member into a second chamber,the second liquid-permeable member disposed at a boundary between thefirst and second chambers, the second liquid-permeable member having afirst surface that faces and is spaced apart from the second surface ofthe first liquid-permeable member, the second liquid-permeable memberhaving a second surface opposite the first surface of the secondliquid-permeable member and contacting the second chamber.
 38. Themethod of claim 37, wherein a pore size of pores of the hydrophobicporous member is 1-150 μm.
 39. The method of claim 37, wherein thehydrophobic porous member is porous polytetrafluoroethylene, porousperfluoroalkoxy, or porous fluorinated ethylene propylene.
 40. Themethod of claim 37, wherein: the immersion liquid is drawn through thefirst liquid-permeable member into the first chamber by coupling theentrance port of the first chamber to a first vacuum system; and theimmersion liquid is drawn through the second liquid-permeable memberinto the second chamber by coupling an entrance port of the secondchamber to a second vacuum system.
 41. The method of claim 40, whereinthe entrance port of the first chamber is a first lumen of a dual-lumenpassage, a second lumen of the dual-lumen passage comprising theentrance port of the second chamber.
 42. The method of claim 37, whereina distance between the second liquid-permeable member and the firstliquid permeable member varies for different portions of the firstsurface of the second liquid-permeable member.
 43. The method of claim42, wherein the first surface of the second liquid-permeable member isconvex.
 44. The method of claim 42, wherein the second liquid-permeablemember is slanted relative to the first liquid-permeable member.
 45. Themethod of claim 37, wherein at least one of the first and secondliquid-permeable members is a mesh.
 46. The method of claim 37, whereinat least one of the first and second liquid-permeable members is asponge.
 47. The method of claim 37, wherein at least one of the firstand second liquid-permeable members is a plate have holes extendingthrough the plate.